题解 | 把字符串转换成整数(atoi)

class Solution:
    def StrToInt(self , s: str) -> int:
        x = 0
        sign = 1
        flag = True
        for c in s:
            if flag and c==' ':
                continue
            elif flag and c=='-':
                sign = -1
                flag = False
            elif flag and c=='+':
                sign = 1
                flag = False
            elif c.isdigit():
                x = x*10+int(c)
                flag = False
            else:
                break
        if sign*x>=2**31:
            return 2**31-1
        elif sign*x<-2**31:
            return -2**31
        return sign*x